Early activation of plasma membrane H super(+)-ATPase and its relation to drought adaptation in two contrasting oat (Avena sativa L.) genotypes

• Published in: Environmental and experimental botany 2010-09, Vol.69 (1), p.1-8
• Main Authors: Gong, Dong-Shan, Xiong, You-Cai, Ma, Bao-Luo, Wang, Tian-Ming, Ge, Jian-Ping, Qin, Xiao-Liang, Li, Pu-Fang, Kong, Hai-Yan, Li, Zi-Zhen, Li, Feng-Min
• Format: Article
• Language: English
• Subjects: Avena sativa
• ISSN: 0098-8472
• DOI: 10.1016/j.envexpbot.2010.02.011

Major objective of this study is to elucidate the effect of early activation of root hair cell plasma membrane (PM) H super(+)-ATPase on drought adaptation in plants. Pot-culture experiments were carried out to determine oat (Avena sativa L.) genotypic differences in water maintenance, osmotic adjustment and PM H super(+)-ATPase activity at the seedling stage. Two oat genotypes with contrasting drought sensitivity, Dingyou6 (A. vernasativa, drought-tolerant cultivar) and Bende (A. venanuda, drought-sensitive cultivar) were subjected to soil drought stress under environment-controlled growth chamber conditions. At 21 days after emergence, water supply was withheld to allow soils in pots to dry. Our results showed that drought-tolerant "Dingyou6" maintained significantly greater RWC and osmotic potential (OP) in roots and leaves, and also had larger root-to-leaf ratios of RWC and OP than drought-sensitive "Bende" along with 14-day drying process, suggesting that drought-tolerant cv. possesses superior root-to-leaf hydraulic conductivity, and stronger regulatory ability to drought stress. Analysis of the PM H super(+)-ATPase activity and the root and leaf osmolyte contents provided further chemical evidence for this result. Biosynthesis of leaf proline and glycine betaine (GB) followed a similar trend as the activities of root hair cell PM H super(+)-ATPase prior to intermediate stress (around 35% FWC). Significant increase in the activity of PM H super(+)-ATPase was observed at the SWC of about 45-50% FWC, without detectable changes in leaf and root RWC simultaneously. This demonstrated that there existed an early-warning response in roots before the onset of significant decrease in plant RWC. Moreover, the interspecific difference in the timing of triggering early response was obvious. Drought-tolerant "Dingyou6" initiated early response at about 50% FWC, but at about 45% FWC for drought-sensitive cv. This study implies that early activation of root hair cell PM H super(+)-ATPase triggers the increased biosynthesis of major osmolytes, which, in turn, leads to the up-regulation of water maintenance system.